1. Field of the Invention
The present invention relates to a portable labeling machine, or the like, and more particularly to a printing platen for use with the portable labeling machine, or the like which platen enables labels, or the like, to be imprinted clearly with averaged imprint uniformity and density.
2. Description of the Prior Art
The printing platen of a portable labeling machine (which will be referred to as a "hand labeler") or of a tagging machine is located so that labels or tags placed thereon may be imprinted with the indicia of a plurality of types which are carried on type wheels or type bands or other type carriers of a printing head. The types are often arrayed in a row across the printing head, and a number of rows of types may be provided along the length dimension of the platen.
Generally, the printing platen is made of hard, i.e. non-deformable in normal use, material, such as a metal plate or a hard plastic.
The printing types for a hand labeler are usually made of an elastic material, such as rubber. As a result, even if the printing surfaces of the respective rows of the types of a printing head (or of the type wheels or bands of the printing head) become irregular or rough or have different heights due to errors during production or due to wear after use, the raised elastic types are depressed when they are brought into contact with the surface of the label upon the printing platen during the printing operation. The types as a whole are flattened when they contact the label surface, so that a clear imprint, having an averaged imprint density, can be effected as a whole.
Types made of relatively hard plastics have recently been frequently used for a hand labeler because of the ease of their production, the reduction in their production cost and their excellent durability, in comparison with the conventional types made of rubber. Sometimes types made from metal are used, for most of the same reasons as hard plastic types are used. In case the types are made of a hard plastic or of metal, the raised types will not be depressed during the printing operation because the material from which the types are made has lower elasticity, as compared with softer plastic. If there are discrepancies in height among the types in a row or among the plurality of rows of types, the more depressed types will fail to contact the label surface or will have a relatively slight contact pressure, so that the imprints corresponding to the depressed types will either not be obtained at all or will be unclear, thus making it difficult to effect a clear imprint as a whole.
Thinness, faintness and uneven density imprints are acceptable to some extent in case the imprints are read by the human eye. But, this can be a fatal defect in the case of a POS (Point-Of-Sales) system, in which the imprint has to be read by an optical character reader requiring clear and highly accurate imprints.